1. Field of the Invention
The present invention relates to an improved drive chuck key.
2. Description of the Prior Art
Drill chuck keys have long been employed to provide convenient and rapid mechanical advantage for closing the jaws of a drill chuck on a cutting bit to hold the bit in place during the cutting operation. As has long been recognized by those skilled in the art, a critical shortcoming of conventional drill bit keys is that such keys typically incorporate a relatively short cross bar for acting as a finger grasp element to provide purchase for the tightening or loosening operation. Such drill chuck keys suffer the shortcoming that the cross bars are typically relatively small, inconvenient and uncomfortable to grasp by the workman's bare fingers for rotation with sufficient force to provide the necessary tightening force for positive and secure tightening of the chuck on the cutting bit to prevent slippage for misalignment during challenging cutting operations.
Oftentimes the workman prefers to tether the drill bit chuck key from an electric cord leading to an electric motor housing or to other components of the motor housing to thus prevent misplacement or loss of the key. Thus, preference has been shown for a compact key which is convenient to store during non-use and which may be easily manipulated into position during a chuck tightening or loosening procedure.
Conventional drill chuck keys thus frequently fail to positively tighten the chuck on the cutting tool thus creating, at worst, a dangerous situation for the workman while operating the drill or, at best, a potential misalignment of the cutting bit which often results in an inaccurate cutting process.
Efforts to solve the problem of inadequate leverage to achieve positive tightening or loosening of a chuck have led to the proposal that the integral key and gear segment be formed with various hand accommodating cross members. However, the cross members, to accommodate the desire for compactness in the key for storage purposes, have been typically of limited size, thus limiting the amount of mechanical advantage provided by such cross member. Chuck keys incorporating various configurations of cross bar hand grasp elements are shown in U.S. Pat. No. Derbyshire 4,186,933.
Other efforts to provide a satisfactory drill chuck key have led to the proposal of an enlarged cylindrical tool formed at one end with a gear segment having a threaded shaft projecting therefrom for threaded engagement with a custom formed threaded bore formed in the gear chuck assembly. A device of this type is shown in Sturgis U.S. Pat. No. 4,462,728. While serving the function of providing for positive engagement with the drill chuck, such devices suffer the shortcoming that the leverage afforded during the bit tightening or loosening procedure is limited by the diameter of the tool itself.
Other efforts to improve chuck keys have led to the proposal of a chuck key incorporating a lever arm having a ratchet mechanism therein with oppositely facing gear and pin elements carried from one end thereof for selective engagement with a drill chuck. A device of this type is shown in Cummings U.S. Pat. No. 4,781,083. Devices of this type suffer the shortcoming that they are relatively expensive to manufacture, are bulky and cumbersome to store and necessitate manipulation of the lever handle even prior to the time that significant forces are to be applied to the tightening action of the drill chuck.
One of the drawbacks of incorporating a crank of any substantial size in a drill chuck key is the consequent problems associated with storage of the chuck key between uses and the inconvenience that would be associated with manipulating the chuck key into position at the time of use. Thus, there exists a need for a drill chuck key which is compact and convenient to store but which will, in use, be adaptable to apply a high degree of tightening force to the drill chuck.